A phase I trial of SON-1010, a tumor-targeted, interleukin-12-linked, albumin-binding cytokine, shows favorable pharmacokinetics, pharmacodynamics, and safety in healthy volunteers

Background

The benefits of recombinant interleukin-12 (rIL-12) as a multifunctional cytokine and potential immunotherapy for cancer have been sought for decades based on its efficacy in multiple mouse models. Unexpected toxicity in the first phase 2 study required careful attention to revised dosing strategies. Despite some signs of efficacy since then, most rIL-12 clinical trials have encountered hurdles such as short terminal elimination half-life (T½), limited tumor microenvironment targeting, and substantial systemic toxicity. We developed a strategy to extend the rIL-12 T½ that depends on binding albumin in vivo to target tumor tissue, using single-chain rIL-12 linked to a fully human albumin binding (FHAB) domain (SON-1010). After initiating a dose-escalation trial in patients with cancer (SB101), a randomized, double-blind, placebo-controlled, single-ascending dose (SAD) phase 1 trial in healthy volunteers (SB102) was conducted.

Methods

SB102 (NCT05408572) focused on safety, tolerability, pharmacokinetic (PK), and pharmacodynamic (PD) endpoints. SON-1010 at 50-300 ng/kg or placebo administered subcutaneously on day 1 was studied at a ratio of 6:2, starting with two sentinels; participants were followed through day 29. Safety was reviewed after day 22, before enrolling the next cohort. A non-compartmental analysis of PK was performed and correlations with the PD results were explored, along with a comparison of the SON-1010 PK profile in SB101.

Results

Participants receiving SON-1010 at 100 ng/kg or higher tolerated the injection but generally experienced more treatment-emergent adverse effects (TEAEs) than those receiving the lowest dose. All TEAEs were transient and no other dose relationship was noted. As expected with rIL-12, initial decreases in neutrophils and lymphocytes returned to baseline by days 9-11. PK analysis showed two-compartment elimination in SB102 with mean T½ of 104 h, compared with one-compartment elimination in SB101, which correlated with prolonged but controlled and dose-related increases in interferon-gamma (IFNγ). There was no evidence of cytokine release syndrome based on minimal participant symptoms and responses observed with other cytokines.

Conclusion

SON-1010, a novel presentation for rIL-12, was safe and well-tolerated in healthy volunteers up to 300 ng/kg. Its extended half-life leads to a prolonged but controlled IFNγ response, which may be important for tumor control in patients.

Clinical trial registration

https://clinicaltrials.gov/study/NCT05408572, identifier NCT05408572.

Flow cytometric analysis of recombinant murine GM-CSF (rmuGM-CSF) induced changes in the distribution of specific cell populations in vivo

The changes in the distribution of granulocytes, monocytes, and lymphocytes in various tissue compartments following subcutaneous (SC) administration of recombinant murine GM-CSF (rmuGM-CSF) in vivo was determined by flow cytometry in time course studies. Balb/c mice were given single, daily SC injections of 1 or 4 micrograms of rmuGM-CSF for 10 days. Flow cytometric analysis was performed on bone marrow (BMC), peritoneal exudate (PEC), and peripheral blood (PBC) cell preparations from mice treated for 1, 3, and 10 days. Dual fluorescence was employed to gate on leukocytes (T200+) and analyze for Ig+, Thy 1.2+, MAC+, and 8C5+ (granulocytes) cells. The analyses indicated that SC-rmuGM-CSF increased the percentage of 8C5+ cells in PBC after 1 day of treatment. However, significant changes in the cell composition of PEC and BMC were not observed until day 10 of treatment and included increases in 8C5+ cells and the myeloid cell population, respectively. Side scatter analysis (cell density) of PBC and PEC indicated that the percentage of the granulocytic cell population increased significantly in rmuGM-CSF treated mice. The changes observed in PEC and BMC appeared to be dose-related whereas those observed in PBC were not. These data clearly demonstrate the utility of flow cytometric analyses for detecting selective effects of cytokines on cell populations that are involved in host defense mechanisms.

Inhibition of graft-vs-host induced immunodeficiency with immunosuppressive therapy

The pathologic features of the acute graft-vs-host disease occurring in unirradiated (C57Bl/6 X A/J)F1 mice injected intravenously with lymphocytes from the C57Bl/6 parent are similar to those reported for other parental----F1 hybrid combinations. When stimulated in culture with concanavalin A, lipopolysaccharide or alloantigen, spleen cells from B6AF1 mice that had been injected 11 days previously with B6 lymphocytes exhibited proliferative responses that were drastically reduced in comparison to the responses of spleen cells from F1 hosts injected with syngeneic lymphocytes. IL2 production in GVH spleen cell cultures was also diminished. Proliferative responses and IL2 production were partially restored in mice given immunosuppressive therapy with azathioprine, cyclosporin A or Sch 24937 a drug whose inhibitory effects on cellular and humoral immune responses in mice have recently been described. Phenotypic analyses by flow cytometry of the GVH splenocyte population indicated that the most consistent change in the GVH spleen was the appearance of an Lyt2+ L3T4+ T cell subset which in the majority of experiments was accompanied by an increase in cells expressing only the Lyt2 antigen. Both subpopulations were reduced in mice that had recovered immunological responsiveness following immunosuppressive therapy. The results suggest that in this GVH model the development of an immunodeficient state is directly related to the induction of an active T suppressor cell population and that such cells are effectively eliminated from the splenocyte population following treatment with some immunosuppressive drugs.

Inhibition of collagen II arthritis by simultaneous administration of concanavalin A and other substances with antigen emulsion

Several pharmacological agents, some of which are known to have effects on the immune system, decrease the incidence of collagen II-induced arthritis when added to the antigen emulsion. Concanavalin A, which has been reported to exert suppressive effects on the immune system in vivo, consistently reduced the immune response to the collagen antigen. These effects were dose and time dependent. The suppressive effects of pokeweed mitogen, tilorone and carrageenan on anti-collagen II responses were somewhat variable. Suppressive activity could be observed with concanavalin A and levamisole when the drugs were injected at a site distant from the collagen emulsion. These studies indicate that local administration of drugs is an effective approach for demonstrating the activity of some agents that may alter the course of collagen II disease through an effect on the immune system.